Impact of the radial profile of atomic nuclei on observables in high-energy collisions

In heavy-ion phenomenology, the nucleon density distribution in colliding nuclei is commonly described by a two-parameter Woods-Saxon (WS) distribution. However, this approach omits the detailed radial structure in the density distribution that arises from quantal filling patterns of neutrons and protons. These fine structures, as estimated by the Skyrme-Hartree-Fock density functional, cause small deviations in heavy-ion observables from the WS baseline, which cannot be captured by simply readjusting the WS parameters. These deviations are dependent on centrality and observable but often exhibit similar shapes for different nuclei. Such fine structures may introduce up to a 25% uncertainty in the measured differences in heavy-ion observables between the ⁹⁶Ru+⁹⁶Ru and ⁹⁶Zr+⁹⁶Zr mid-central collisions from the STAR Collaboration.